Abstract

Several database (DB) applications are temporal of nature and require a special treatment. In particular, inthe field of concurrency control (CC) which takes new dimensions when applied to temporal DB (TDB). TheCC algorithms proposed for TDB have tried to find solutions for the CC to improve their performances.Especially, they have tried, by benefiting from the characteristics of the TDB, to decrease the degree ofconflict, and this by the use of à priori knowledge or the reduction of the granule sizes. But these algorithmshave not reached the fixed objectives. To contribute to the edification of a CC component suitable for TDB,we propose in this paper a complete study of access concurrency control in TDB. We have chosen to buildour algorithms according to the optimistic methods, which are, in our opinion, more suitable for TDB thanthe pessimistic methods. Indeed, our optimistic algorithms can exploit the temporal specifications to reducethe granule size and then to minimize the conflict degree. Moreover, they can detect, as soon as possible, allthe conflict cases. By using the end of transaction marker technique, they have the merit to reduce to themaximum the period during which resources are locked in the validation phase. To be sure that ouralgorithms operate correctly, we have carried out a formal verification, based first on the serialization theoryand next on the SPIN model checker. Then, we have made a performance evaluation vis-à-vis of other wellknownconcurrency control algorithms based on optimistic and pessimistic approaches, to show that ourpropositions ameliorate the performances in the large majority of the cases.

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